The present disclosure relates to an image forming apparatus capable of forming an image by electrophotography.
An image forming apparatus, such as a printer, which is capable of forming an image by electrophotography is known. In the image forming apparatus, a photosensitive layer portion of an image carrier such as a photosensitive drum is charged by a charging portion such as a charging roller. On the photosensitive layer portion of the image carrier that has been charged by the charging portion, an electrostatic latent image is formed by light applied thereto from a light irradiation portion. Then, the electrostatic latent image formed on the photosensitive layer portion of the image carrier is developed, for example, by toner that is supplied from a developing unit and charged with the same polarity as the charge polarity of the photosensitive layer portion. Thereafter, the toner image developed by the developing unit is transferred onto a transfer target medium by a transfer portion, such as a transfer roller, to which a voltage having polarity opposite to the charge polarity of the toner is applied. As the photosensitive layer portion of the image carrier, a photosensitive material is coated on a base portion. As a method for coating the photosensitive material onto the image carrier, a dipping method or a ring coating method is known.
Meanwhile, the toner image formed on the photosensitive layer portion of the image carrier may be transferred onto an intermediate transfer belt, which is the transfer target medium, by the transfer portion. The intermediate transfer belt includes a base layer portion and a surface layer portion. For example, the base layer portion is formed of a thermoplastic resin, and, as the surface layer portion, a thermosetting resin which is a surface layer material is coated on the base layer portion. As a method for coating the surface layer material onto the intermediate transfer belt, a dipping method or a ring coating method is known.
In addition, in such a type of an image forming apparatus, the toner image formed on the intermediate transfer belt is transferred from the intermediate transfer belt to a sheet by the transfer roller. For example, the transfer roller is provided at a position opposing a driving roller, which causes the intermediate transfer belt to run, so as to be in contact with the intermediate transfer belt. Moreover, the transfer roller is biased toward the driving roller in order to obtain, at a nip portion formed between the transfer roller and the intermediate transfer belt, a nip pressure required for transfer. Here, the transfer roller can be rotationally driven by a driving force transmitted from the driving roller via a first gear provided on a rotation shaft of the driving roller and a second gear provided on a rotation shaft of the transfer roller.